Manufacture of paper



No Drawing.

Patented June 16, 193 1 UNITED STATES PATENT. orrlcs HAROLD Bil AFTON, F LAWRENCE, MASSACHUSETTS, ASSIGNOR TO RAFFOLD PROCESS GORPORATIOIL A. CORPORATION OF MASSACHUSETTS v MANUFACTURE 01Ev PAPER This invention relates to theimanufacture of paper. v t v The principal object of my invention is to provide a method whereby paper may be manufactured to contain an amount of filler greater than is feasible by the; usual procedure.

An important'object is to provide a method whereby in the papermaking operation a smaller proportionof the filler than is normal passes through the web-forming device into the white water.

' A further object is to provide a method whereby paper of very high'filler content may be manufactured.

Other objects and advantages of my invention will-become apparent in the course of the following description.

The ordinary method of manufacturing 89, paper is to mix the fibre and fill-er in the beater or like machine, together with alum, or alum and size, and then after suitable treatment in the beater, to pass the mix through the subsequent apparatus and mechanical. 2 treating equipment such as the chests and the jordan, and thento dilute the mix atthe mixingbox with white water, e. g. tray water from the machine, and'with other water if desired, and finallyto' conduct thediluted mixto the web-forming device of the paper machine "Here'the web is vformed with simultaneous removal of the white water,

which normally contains a relatively larger proportion of filler to fibre than does the stock fed to the web-forming device.

The retention of filler in paper has always beena matter for serious consideration in papermaking. In the former prevailing practice, which has now been superseded to 40 white water (excepting part of the tray waa considerable extent, practically all of the ter) flowed to waste and hence a considerable proportion of the filler employed in the beater escaped in the white water and was lost.

This condition was greatly improved by the introduction of'sav -all systems, such as by sedimentation, filtration, deckering, or the like which usually recover a lar' e propor tion, and in some cases practica 1y all. of

o the solids suspended in the white water.

Application filed November 27, 1928 :Serial No. 322,291.

. 7 Such save-all systems usually return the recovered stock to the heater or to one of the the wastage of filler. It has consequently reduced the amount of filler required to be used i in the beater for a given filler content in the paper. Moreover it has provided a means by which a relatively higher percentage of filler in the finished paper may be obtained 00 in regular commercial production than was formerly feasible, as ity is now possible to carry a higher percentage of filler to fibre circulating in the machine waters without excessive losses.

However even with the present save-all systems there is a practical limit to which the filler content of paper may be raised for any given set. of conditions. This results from the fact that when the filler content of the'stock is pushed beyond a certain point filler, and moreover underthese conditions the save-all systems rapidly become inefiicien-t and fail to recover the greatlyincreasedfiller content of the white water.

For instance in magazine paper, with a sulphite-soda furnish, with several hours beating, and machine speed between 350 and 400 feet per minute, using a sedimentation save-all system, the filler content runs about 22% as a maximum. With a furnish consisting of approximately equal parts of sulphite pulp, soda pulp and old paper stock with from 1 to 2 hours beating, with a machine 35 speed of approximately 400 feet per'minute, using a filtration save-all system, the filler content runs about 24% as a maximum.

It will be understood, of course, that with varying conditions of hydration of the stock,- and varying kinds of fibre and grades of paper to be made as well as varying machine speeds, amounts of sizing,'alum, and the variation of the numerous other factors in papermaking, that the filler content in any given case mayvary somewhat one way or *the other, "but in making, for instance, a

magazine grade of paper the above represent approximately the maximum filler contents i which can be obtained in regular machine operation.

I have discovered that it is possible to increase the filler content of paper, above that percentage normally obtainable when the v usual methodis employed, by the expedient paper machine,

of adding alum to the paper mix at or subsequent to the point at whichthe mix is diluted prior to delivery to the web-forming device, that is, in other words, at the Wet end of the pape machine. v

I have found for instance that a given amount of alum added in the beater to a fibrous mix containing filler will not produce a paper having as high a filler content as will an equal amount of alum added at the wet end of the papermachine to a similar fibrousfiller mix. The difference may range from as low as 1% in some, cases up to 3 or 4% in other cases, and in still other cases the difference in percentage may bemuch higher. Even the lower mentioned difference of 1% is of great economic importance, amounting to a savingof $30 to per day in a 100 ton mill (assuming no change in fibre furnish), and of course the saving mounts proportionately with theincrease of the difference in filler contentthat it is possible to obtain.

Of course part of the alum may be added in the beater and part at the wet end of the but .I have found that the maximum results are obtained by the use of all the alum at the wet end of the paper machine.

In the practice of my invention my preferred method is to add the fibrous materials and filler, together with size if any is-to be I it is to be diluted prior to the delivery employed, in the beater, subject the mix to the usual mechanical treatment, then pass it through the usual steps and mechanical treating machinery up to the point at which to the web-forming device. this point I add the requisite amount of alum, preferably continuously, preferably in dilute aqueous solution, either in fresh water, or admixed with a diluting liquid.

I have found that if the alum be added when the fibrous mix containing the filler is in relatively concentrated condition, even after it has left the-beater, and particularly in places where the mix would be subjected to agitation such as is normal in the stuff chests, this effect of increased filler retention is deteriorated, and thus to procure the efiect it is necessary to add the alum under such conditions that there is a minimum'of intimacy as well as time of contact of the constituents of the mix, namely, at the wet end of the paper machine. I have also found that prolonged agitation even in the dilute state injures the effect,

time that the mix remains in the dilute condition inth'e ordinary papermaking procedure any At or subsequent to Of course if desired the filler as well as the size may also be added atthe wet end of the paper machine, but the important point is that the alum must be added atthis oint, and 'I therefore consider the addition of the filler and size together with the alum at this point the equivalent of adding the filler and size to the fibre in the beater.- have not found that the presence of siz ng hasany marked effect on the filler retention when my process is employed. The alum seems to be the controlling factor.

My process results in a greater retention of filler in the paper and hence, under any given set of circumstances, in a. smaller amount of filler passing through into the white water, with a corresponding lessened diflicult'y in operating save-all systems course, to obtain a higher filler content in the paper than formerly, where a substantially closed white water cycle is employed, more filler in .proportion to fibre than formerly should be used in the furnish.

In the above description of my preferred practiceI have assumed a use of alum no greater than that regularly employed under given set of conditions. However, I have found that it is sometimes very desirable to increase this amount of alum, and thereby still further increase the percentage of filler retained in the paper. The savlng obtained by increased filler content normally more than offsets the increase alum cost. This increased use of alum is indicated up to the point Where other, factors negative the desirability of further increased filler content, such as strength, two-sidedness, or the like. The amount of ,extra alum which is desirable to be added may also be limited to some extent by the desire not to get the stock too acid.

Instead of alum, I may 0 aluminum such as the .chloride, or with a certain measure of success, other metallic salts such as zinc salts, for example zinc sulphate.

By the word filler I mean such inorganic loading as clay, talc, or the like, which is of manufacture of all types and 'of all p weights and thicknesses, which contain as an but from a practical standpointthe essential constituent a considerable amount of prepared fibre and which are capable of being produced on a Four drinier, cylinder,

use other 'salts of ltlu or other forming, felting, shaping or moldin machine.- x

p y the term wet endfof the paper machine I intend to include those instrumentalities employed. in paper manufacture by which and/or.- in which a relatively concentrated paper mix is diluted, and treated, confibrous material consisting of sulghite tion,

.and pro ortioning devices, rifilers, troughs,

0f contact, and t veyed or fed "up to the point of web-formasuch as the mixing box, regulating screens, ead boxes, inlets, and'the like,

While I have described in detail the preferred embodiment of m invention, it is of course to be taken as 'ilfhstrative on].

9. The method of producing filled paper comprisinge mixin fibrous material and filler in a ater,,a ding a salt of aluminum and B not limiting, as it is to be understoo that detailsof procedure,'-kinds of material used in furnishes, proportions of ingredients, and without departing rom thesgirit of may-in verritiim .or the scope of the su joined claims.

arrangement of steps may be widely varied 1. The method of producing filled paper, I

comprising adding a metallic salt to a mix com rising fibrous material and filler under the minimizing of time ereafter making paper con itions favorini therefrom. a

- 2. The method of comprising adding a metallic salt to am comprising fibrous material and filler under conditions favoring timacy and time o contact, and thereafter makinipaper therefrom. e,

3 T e method of producing filled aper, comprising adding-a metallic salt at t e wet end of the paper machine to amix comprisproducingfilled paper, I

the minimizing of in- I ing fibrous material and, filler, and there- Y after x'naking'paper therefrom. r i 4. The-methodof producing filled paper, q

wet end 0 the paper machine'to a mix comp ."comprising mixing fibrous material and filler 'i n' a beater; adding ag'meta'llic salt at the wet we, and thereafter ee mzrw e-.-

comprisin addinga salt of aluminum atthe after making paper therefrom.

prising-fibrous material and filler, and there- '5. The method ofproducing. filled pa er comprising adding alum at the wet en of the. paper machine to a mix comprising fibrous material and filler, andthereafter makin paper therefrom. a

6. fie method of producing filled aper,

end of the paper machine to a mix' compris comprising adding a metallic salt at t a wet 1n 'fibrous material consisting of sulphite' I pa and Soda plilp and fille' gand thereafter gma 'fipapert refrom'. 7. e method ofproducing filled aper,

compnsmg' adding a metallic salt at e wet end of the paper machine to a mix comprisuiiig soda pulp, and oldpaper stock an filler, thereafter making paper therefrom. v '8. The method of producing filled paper n fciftlroiqmr'er ma'chin 

